A small portion of the radio frequency (RF) spectrum is assigned to each communications carrier. The assigned spectrum, therefore, must be used efficiently in order to allow the maximum number of frequency users to have access to this spectrum. Multiple access modulation techniques have been developed to provide optimum utilizing of the RF spectrum. Examples of such modulation techniques include time division multiple access (TDMA), frequency division multiple access (FDMA), and code division multiple access (CDMA).
There is a wide variance in the performance of wireless networks. A conventional wireless cellular network, covers a relatively large geographical area but provides a relatively low bandwidth. Such wireless networks use regulated portions of the radio spectrum and are shared by many users. The infrastructure costs of wireless networks are relatively high due to the size and complexity of the cellular network equipment.
Other wireless networks, such as CDMA2000-EV-DO/DV networks, offer higher bandwidth and enhanced data services, such as web browsing. However, these networks also pack many users into a relatively small portion of the regulated spectrum. Other types of radio networks are adapted to improve spectral efficiency with increased and smaller coverage areas. For example, an IEEE 802.11x (or Wi-Fi) network may transmit at speeds up to 11 Mbps using a Direct Sequence Spread Spectrum (DSSS) mode or at speeds up to 54 Mbps using an Orthogonal Frequency Division Multiplexing (OFDM) mode.
An access point conforming to an IEEE 802.11x (e.g., IEEE 802.11b) network may cover an area of a few hundred feet in diameter. Each such access point is connected to a larger network (e.g., Internet). In order to cover larger geographical areas, a relatively large number of IEEE 802.11x network access points and a relatively large wire-line back haul networks are required. In part, due to the back haul costs, the resulting IEEE 802.11x based network may thus be more expensive to set up and operate than a similarly based wireless network. In other words, many tradeoffs often exist between and among the coverage areas, the maximum bit-rates, and the costs associated with different types of wireless networks.
Demand for high bandwidth and quality of service (QoS) associated with mobile communication devices with full roaming capability is on the rise. One known communication device includes a cellular communication module adapted to enable communication using wireless cellular networks as well as a Wi-Fi communication module adapted to enable communication using a Voice over IP (VoIP) protocol. In such devices, to change the communication mode from cellular to VoIP or vice versa, the user has to manually change the device's setting by, e.g., pressing one ore more keys.
In yet other communication devices known to be under development, to switch the communication mode from, for example, cellular to VoIP, the cellular network first detects the position of the mobile communication device to determine whether the mobile communication device is in a Wi-Fi area. If it so detects, the cellular network sends a switching signal to the mobile communication device to enable the communication to continue the communication using the VoIP protocol. However, obtaining and maintaining accurate position of many mobile communication devices concurrently poses a challenging task. Consequently, in such systems, the switching of the call from cellular to VoIP or vice versa may result in the loss of the call.